1. Field of the Invention
This invention relates to an energy-absorbing fastener system, and particularly to such a system usable to fasten an automotive trim panel to a structural member, such that the trim panel can deflect toward the structural member to absorb impact energy when a load is incident on the trim panel.
2. Prior Developments
In order to reduce the effects of impact against a trim panel, it has been proposed to incorporate energy-absorbing devices into the trim panels. In many vehicles the trim panel absorbs some impact energy, while the fasteners act as hard points incapable of absorbing impact energy. In some cases, the energy-absorbing function has been built into the fasteners used to retain the trim panel in spaced relation to an associated outer structural member. The present invention is concerned with a trim panel fastener adapted to absorb some of the impact energy.
U.S. Pat. No. 5,169,204, issued to J. Kelman, discloses a vehicle door system wherein inner and outer panels are spaced apart by fasteners that include shock absorber devices for absorbing impact forces. In one case, the shock absorber comprises a viscous gel contained in a piston-cylinder assembly for extrusion through small openings in the piston. In another case, the shock absorber comprises a hemispherical enlargement formed of an elastic material so that it undergoes a squeeze deformation in order to pass through a restricted opening in the outer panel.
U.S. Pat. No. 5,362,102, issued to U. Hajek et al, discloses an impact energy-absorbing fastener that includes a fastener pin having three axially spaced circumferential ribs designed to undergo radial squeeze deformations to pass through a central hole in a fixed structural member. The energy absorption during the stroking action (also referred to as snubber action) is discontinuous and irregular. While each projection is expanding to its original configuration the deceleration rate of the panel will vary resulting in a less than optimized system. Additionally, at column 2, lines 34 and 35, the patentee indicates that the normal position of the fastener is defined by stops; such stops would likely interfere with the desired stroking action of the fastener.